Brian Johnson has been AC/DC’s singer ever since the 1980 death of Bon Scott. But last year, doctors told Johnson that he had to stop touring or risk hearing loss. This led to the surreal spectacle of Axl Rose touring with AC/DC. Johnson, meanwhile, insisted that he was not retiring. And true to his word, Johnson showed up onstage at this past weekend’s Reading Festival in the UK. But Johnson wasn’t performing with AC/DC. Instead, he showed up with, of all possible bands, motherfucking Muse.

Last night, the prog warriors Muse headlined Reading. And during their encore, as Rolling Stone points out, they brought out Johnson, who still sounds more or less like himself, to sing a spirited rendition of “Back In Black.” This was Johnson’s first time performing an AC/DC song since just before his March 2016 diagnosis. I hope he didn’t fuck up his hearing to make the appearance. Watch a fan-made video below.

Rolling Stone also points out that Johnson performed “Money (That’s What I Want)” with Robert Plant and Bad Company’s Paul Rodgers in Oxford back in May. I have no idea how we missed that one.